In wireless communication systems, hybrid automatic repeat request (HARQ) is utilized as an error-control method in which a data packet is repeatedly transmitted until the receiving device successfully decodes the packet. In some systems, the data packet may be subdivided into two or more subpackets transmitted at a varying code rate for each subpacket in order to help support HARQ transmission. In some HARQ processes, a retransmission bit may be mapped into the same layer of the constellation that is highly modulated, which may degrade decoding performance on the receiver side. In order to prevent retransmission bits from being allocated into the same level as the initial transmission bits, constellation rearrangement schemes may be employed in which the data bits may be rearranged from one transmission to the next transmission. However, with such schemes the adjacent bits in same transmission may still be mapped into the same constellation layer as a highly modulated data, which may impact the decoding performance on the receiver side.
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